This invention relates to a new therapeutic polymeric foam dental appliance which can be utilized in the treatment of teeth, a method of preparing such an appliance, a method of providing therapeutic treatment for teeth utilizing such an appliance, and a sterile, prepackaged therapeutic appliance in a ready to use form for use by dental professionals.
During the first four decades of this century, the search for the etiologic factor responsible for endemic dental mottling in localized regions of the United States led to the discovery that fluoride is a potent cariostatic agent. Thereafter, it was determined that topically applied fluoride could reduce the rate of dental caries in many individuals. Today, a wide variety of fluoride-containing products are available for professional use. In addition to the many fluoride containing dentifrices and mouthwashes, there are a variety of dental trays which fit into the mouth and are used to apply a fluoride gel to the teeth.
A current problem with fluoride products which utilize fluoride gels which are applied to containers whose geometry resembles the general shape of the teeth is that an excess of fluoride is used which ultimately can pass into the gastro-intestinal tract, possibly resulting in acute fluoride toxicity. Victims of fluoride toxicity exhibit symptoms which include nausea, vomiting, and burning or cramp-like abdominal pains. Furthermore, there may be excessive salivation and tearing, mucous discharges from the nose and mouth, generalized weakness, paralysis of the muscles of swallowing, carpo-pedal spasms or spasms of the extremities, or tetany. In severe cases the patient may have convulsions, a weak pulse, lowered blood pressure, or depressed respiration.
Topical fluoride gels which are applied in trays that are generally shaped to the maxillary and mandibular arch are, in most cases, acidified with phosphoric acid to a pH of about 3.5 and are called APF (acidulated phosphate fluoride) gels and contain fluoride at concentrations of 1.23% or 12,300 ppm. In other words, each mL of gel contains 12.3 mg of fluoride. Most commonly, fluoride gels are supplied to the dentist in 500 mL bottles which contain over 6000 mg of fluoride. The gel trays are supplied separately and are filled individually for each treatment. The common fluoride gel treatment is applied to the dental arch for a period of four minutes. The average quantity of APF gel introduced into the mouth is in the vicinity of 5 mL, but may be as much as 12 mL, thus providing a corresponding amount of fluoride between 62 and 148 mg. A lethal fluoride overdose would be 60 mg or 4.9 mL for a two year old with an average body weight of 12 kilograms.
It has been demonstrated that the fluoride concentration at the enamel-oral interface is of critical importance in the dynamics of demineralization and remineralizaton (Fejerskov et al., Acta. Odontol. Scand. 39:241, 1981). Clearly, there is a relationship between fluoride concentration in the oral fluids and the action of fluoride on enamel and its environment. Numerous investigations (Le Compte and Doyle, J. Am. Dent. Assoc. 10:357, 1985; More et al., AADR Progr. & Abst. 62:837, 1983; Le Compte and Doyle, J. Dent. Res. 61:1397, 1982; Le Compte and Whitford, J. Dent. Res. 60:776, 1981, and 61:469, 1982; Ekstrand et al., Caries Res. 15:213, 1981; Ekstrand and Kock, J. Dent. Res. 59:1067, 1980; Owen et al., IADR Progr & Abst. 58: No. 1256, 1979; Ekstrand et al, Clin. Pharmacol. Ther. 23:329, 1978) have documented substantial oral retention and ingestion of fluoride following professional application of APF gels topically in children and adults.
The purpose of professional fluoride treatments is to benefit the tooth enamel by a topical effect. In an ideal topical application procedure, the patient would swallow no fluoride. In studies by LeCompte (J. Dent. Res. 66:1066, 1987), the amount of fluoride recovered from the mouth and that retained in the mouth were determined after four minute treatments. A foam-lined tray was used for the treatment with 49.2 mg of fluoride being applied to the teeth. An average of 39.3 mg of fluoride was recovered with the trays and 9.9 mg of fluoride was retained in the mouth. After one minute the patient expectorated an additional 6.8 mg of fluoride leaving a dose of 3.1 mg. Englander et al. (J. Am. Dent. Assoc., 75: 638, 1967) showed that less toxicity exposure resulted when smaller amounts of gel could be used in trays which were custom fitted to the teeth. Such custom trays required only five to ten drops because of the intimate contact between the tray and teeth surfaces. It is recommended that no more than two grams of gel be used in a gel tray application. Newbrun (J. Dent. Res. 66:1084, 1987) has suggested that the amount of fluoride gel should not exceed 1.5 grams.
In addition to the above mentioned toxicity problems, it has also been suspected that with current fluoride gel treatments, the gelling agents utilized may inhibit the efficient transfer of fluoride ions to the tooth surface.